My car is a 2005 audi a6, 3.0l CVT. Been having some intermittent EPC errors since last year.

This is the usual case scenario.

I'll drive the car for a couple of km (usually just less than 2 km), and then the EPC error will come out. when it does the car shakes terribly. RPM jumps from 900rpm to 1100rpm for some time, until you close the car, and let it "rest" for a minute and restart. if you "try" to drive it, it is in limp mode. barely touching 10 km/h on almost 50% throttle.

This problem came out almost 6 months ago, and since then, I've changed the throttle body. (as advised by the dealer.) [1st trip to dealer]

I did have a second opinion in a 3rd party shop before I thought of bringing it to the dealer: this is what vagcom showed:

Weird thing is, this message by vagcom does not always appear. it says adaptation not started, but the dealer says they have adapted the throttle body already. long story short, nothing the shop did ever changed anything, so I brought it again to the dealer.

I've changed the alternator this time (again as advised by the dealer). Sparkplugs have been changed, injectors were cleaned. ignition coil housings were replaced by dealer too. [2nd trip to dealer-3 months after the 1st]

Now, it still happens. Not as bad shaking like before everytime it happens, but when it comes out, they come out twice or even thrice in less than a 3km ride. (the EPC error has happened 7-8 times since, within 500km of usage, used for almost 3-4 times a week in 6 weeks. not everytime it shakes, but it has shaked twice or thrice.) {in fairness, I feel that idle and shifting is smoother.}

Something I saw this time (actually a while ago), I drove the car, warmed up for a minute or two. and left my place, 1 km (2 minutes) of driving later, I come to a halt for a stoplight. I put the car in neutral, and my idling is fixed at 900rpm. radio is on, air conditioning is max at 12. after a few seconds, i feel something and I see the rpm drop to 680rpm, I knew then and there the epc light is coming out. it did. *note I was on neutral.

I am now planning to have the battery changed. (from 80mah to 100mah if its any difference). It was 2007 since the battery was last changed by the dealer. - BUT, it has logged only 12,000 km for the past 5 years. who knows, it might be a voltage issue. (I have never had any issues with starting - but just so I can eliminate this probability) [this will be my 3rd trip to dealer- 2 months after the 2nd.] Note: I live in a tropical country and the current temp is 35 degrees celsius. might have some relation to the battery voltage potentially not being able to keep voltage stable.

For the past 6 months, I've barely logged 1000 km into the car since I fear the car will again get an EPC light. I've never used it long distance. (maximum would be 20 km away - I live near where I work but I feel this is such a waste, should I even bother to change anything and spend more dollars or should I just give up and sell the car. I do feel that I am closing in on the problem hence I am still pursuing.)

I had the same or very similar problem on my 2007 S6 that drove me crazy for a couple of months. ESP/EPC lights come one, car shakes, and then goes into limp mode. I had the same codes in vag com. I also bought a new throttle body and it did not fix the problem.

Finally I replaced the 6 wire connectors and wire adapter to the throttle body and that fixed the problem. It appears the contacts would loose connectivity and throw the error code even though a electrical continuity test I did showed everything was fine.

You can take it to audi but since my friend is an electrican we did it ourselves. He cut the ends off, stipped wire to desired length and put on new ends. We did have to solder the connections since I did not have the professional audi crimping tools.

I didn't take many pictures but have one with the wires cut. Just remember which color wire goes where.

I had the same or very similar problem on my 2007 S6 that drove me crazy for a couple of months. ESP/EPC lights come one, car shakes, and then goes into limp mode. I had the same codes in vag com. I also bought a new throttle body and it did not fix the problem.

Finally I replaced the 6 wire connectors and wire adapter to the throttle body and that fixed the problem. It appears the contacts would loose connectivity and throw the error code even though a electrical continuity test I did showed everything was fine.

You can take it to audi but since my friend is an electrican we did it ourselves. He cut the ends off, stipped wire to desired length and put on new ends. We did have to solder the connections since I did not have the professional audi crimping tools.

I didn't take many pictures but have one with the wires cut. Just remember which color wire goes where.

Feel free to ask questions.

Hi bud,

This is actually the next thing I'm hoping to do post battery change - look at the wiring harness. I figured since I've already changed the throttle body and the epc unit, this should possibly be the next.

Is this exactly what happened to you? Any chance you can shed some more light? Do I need to buy something from Audi? My problem is.. The Audi dealer here doesnt sell any part if they are not the one installing it. Quite irritated with the amount I spent and still not be able to fix the car. I am thinking how I can "explain" doing this. Knowing them, they'd tell me to just change everything.

I bought the head/housing from audi, part number 1J0-973-713 and the wire connectors I bought from ecs tuning. This looks very clean as all the work is hidden in the housing.

You can also buy 3 wires from audi, part number 000-979-131-E and cut them in half to get 6 pieces and shorten them as desired. You then insert the 6 wire connections into the housing, cut the end of the wire harness, strip as necessary and then use a crip connector to join the wires together. I think this is the way audi would fix the harness.